GUIDE: Changing your stat, coolant and water pump

Your coolant performs several jobs including;

1. It stops water from freezing in winter which will then expand and potentially crack cylinder heads and blocks as well as springing leaks in pipework
2. Dissipates heat generated by the engine by circulating the coolant it through the radiator
3. Prevents corrosion of the metal in the cylinder head/block waterways
4. Via the thermostat it regulates the temperature of the engine and ensures it warms up quickly and evenly by pumping the coolant around

Without coolant in the system the car will overheat and can warp cylinder heads etc. I strongly advise you use deionised water in your anti freeze/water mixture because tap water has quite harsh corrosive properties and will eat away at the cooling system. Don't get me wrong, you can get away with this for years but it simply isn't as effective as it could be.

Thermostats and water pumps are the serviceable items. I'd do a stat every year or so (each coolant change) and a water pump about 3-5 years but while you drain the coolant you can easily c the condition of a pump.

Step 1 - Switch your heaters to warm, take the top of the coolant reservoir and disconnect the bottom radiator hose. To do this you should jack the car up a little so you have easy access, make sure you're working on a COLD system, don't change the coolant on a hot car unless absolutely necessary and if so, take great care when dealing with super heated water.



Step 2 - Once you've slackened the jubilee clip and removed the bottom rad hose, coolant will come gushing out so catch this in a bucket or something similar. Remove the two 10mm bolts holding the thermost housing on (do the bolts in stages, don't just slacken one then the other)



Step 3 - With the rad hose off and the 2 bolts out, the stat cover will just pull away

Step 4 - Have a look at where the cover used to be and you'll now see the thermostat



Step 5 - Push the centre of the stat up to allow the coolant to spray out into a suibtable vessel for proper disposal



Alternatively you can remove one of the hoses off the water pump if you want to preserve your stat

Step 6 - Use a flatblade scredriver to ease the thermostat out of the housing

Step 7 - Now we move onto the water pump, before we take the pump out we need to remove the alternator. Remove the 13mm adjuster using two 13mm spanners/sockets (disconnect the multiplug at this stage if attached)



Step 8 - Use a 1/4" drive ratchet with a 13mm socket to remove the pivot bolt (picture 1). Once the bolts is slack a screwdriver may help to push it out (picture 2).




Step 9 - With the alternator slackened off completely, hook the belt over the pulley and remove it

Step 10 - The alternator should now be removed (slide it up and down as you pull it away from the engine if it is tight)



Step 11 - You now have good access to the water pump so we can detach the remaining two connections (we already removed the stat housing). You can do this with a flatblade screwdrive on the jubilee clips (picture 1) if they are in good condition. Mine were badly corroded so I used a 6mm socket (picture 2)

Step 12 - With both jubilee clips slackened/removed, use a flatblade screwdriver to help break the seal whilst wiggling the hoses up and down and pulling them away. Be careful herer not to damage the rubber hoses, they may be quite brittle.



Step 13 - Once the hose is removed you are just left with the 4 big bolts holding the housing to the block and a small 10mm nut attaching the timing cover



Step 14 - The first picture shows the top 2 bolts to remove (13mm) and the second picture shows the bottom two (one with a socket on and the other in the middle of the picture). Progressively slacken all of these then remove them

Step 15 - The bolts are different sizes so here's a picture for reference but try and keep them in the right order if possible



Step 16 - Remove the final fixing which is a 10mm nut holding the pump to the timing belt case

Step 17 - The pump's pulley needs to come off now to allow us to slide the stud through the hole in the timing case (where we removed the nut in step 16). To do this I simply wedged a pry bar as shown in picture 1 and then cracked off the 3 allen key fittings (picture 2)

Alternatively, use mole grips or similar to hold two of the allen key nuts whilst you release the third and do this for each one

Once you've removed the 3 allen key bolts you can remove the pulley (third picture) but it may need a tap with a hammer

NOTE: the pump was changed so you might find you are able to removed the timing belt cover's bolt and then take the aseembly away as a whole without separating the pulley

Step 18 - Now slide the water pump away from the engine (if stuck, tap it with a rubber mallet) and remove it from the car




Step 19 - Remove the o ring if it is left behind on the cylinder block as opposed to being on the pump itself



You should use a scouring pad (or wire wool if lots of limescale build-up is evident) to clean the block once the pump is removed. This will improve the ability for the new pump to seal

Step 20 - If you want to try and disassemble the pump then work your way round these 10mm bolts. Warning, they will probably shear



Step 21 - You might well end up with something like this, a whole bunch of broken bolts and not much joy!



Step 22 - With a bit of persistance and a drill + large haammer I managed to open up mine up to show you the internals

Step 23 - This is the impellor which is the bit that spins around and pumps the coolant around the engine



Step 24 - This is the housing (similar to a turbo) that directs the coolant flow

Step 25 - A new pump from GSF will set you back less than ?30 although you can buy the pump without the 'backplate' which is the bit from step 24. I don't recommend this at the money it costs for a complete unit

Step 26 - If you have the time, wire brush the pulley and paint it to freshen it up



Step 27 - Fit the O ring that mounts between the pump and the cylinder block (included with the pump)



Step 28 - Get yourself a new thermostat (approximately ?5)

Step 29 - Fit it into the water pump housing as shown



Step 30 - Place the second O ring over the stat



Step 31 - Make sure the seal sits flush all the way round

Step 32 - You may need to clean up the thermostat housing if it's anything like the condition mine was in



Step 33 - Fit the housing onto the pump as shown and refit the two 10mm bolts



Step 34 - Replace the jubilee clips on any worn hoses

Step 35 - Before refitting the pump, backflush the system by holding a hose in the cylinder block (picture 1) and then the bottom rad hose (picture 2). When doing this, try to block the pipes with one hand so that you build up a body of water in the engine before you let it come out, a carrier bag around the hose is a good way of making the hose seal in the engine block




Step 36 - Now offer up the water pump and tighten the four 14mm bolts in stages

Step 37 - My new pump didn't have the 10mm bolt fitting for the timing case but check this on yours

Step 38 - Refit the 3 hoses and tighten the jubilee clips




Step 39 - Now it's time to fit the pulley again, use the three allen key bolts you removed previously

Step 40 - My new pump made the pulley sit too close to the timing cover so I had to space it with washers as shown. If you need to do this, insert the 3 allen key bolts into the pulley then put 1 or 2 washers over each of the bolts before popping it into position on the pump itself. Then hold two of the bolts in place whilst screwing the third in



Step 41 - Once complete, check that the pulley is free to rotate without interfering with the timing cover



Step 42 - Now slide the alternator back into place and pop the long bolts through. Hook the fan belt over the crank pulley, water pump and alternator

Step 43 - Fit the adjustment bolt until it is almost tight then pull the base of the alternator up and towards the front of the car (hard) with one hand and then tighten the bolt with the other. Once finished, there should be very little deflectino when you press the fan belt

Once done, you can tighten the other long nut you slide through with a 13mm 1/4" socket



Step 44 - Fill the system with anti freeze and deionised water



Step 45 - As the car heats up, make sure you get heat in both the top and bottom rad hoses (to show the stat works) and squeeze the top hose to force air out. All the while ensure you have a good level in the overflow bottle

check your pms bud

Thanks for the comments, PM back